Pre-clinical investigation of protective effect of nutraceutical D-glucosamine on TNBS-induced colitis.

OBJECTIVE: The level of precursors involved in the biosynthesis of glycosaminoglycan (GAG), glucosamine synthase, and N-acetyl glucosamine (NAG), are significantly reduced in inflammatory bowel disease (IBD). This results in deficient GAG content in mucosa, which eventually disrupt the gut wall integrity, provoking abnormal immunological responses. This is characterized by colossal liberation of inflammatory mediators including tumor necrosis factor-alpha (TNF-α), interleukins (ILs), and reactive oxygen species (ROS) provoking colonic inflammation. D-glucosamine (D-GLU) is reported to suppress oxidative stress, and pro-inflammatory cytokines and acts as a starting material for biosynthesis of NAG. The potential of D-GLU and its combination with mesalamine (5-ASA) was investigated in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-instigated IBD in Wistar rats. MATERIALS AND METHODS: Standard and test drugs were given orally for 5 d to separate groups of rats. Colonic inflammation was evaluated by disease activity score rate (DASR), colon/body weight ratio, colon length, diameter, colon pH, histological injury, and score. Inflammatory biomarkers IL-1ß, TNF-α, along with reduced glutathione (GSH), and malondialdehyde (MDA) were assessed. RESULTS: Combination of D-GLU + 5-ASA significantly ameliorated severity of colonic inflammation by lowering DASR (p < 0.001) and colon/body weight ratio (p < 0.001), restored the colonic architecture and suppressed the histopathological score (p < 0.001), along with the absence of major adverse reactions. The combination suppressed the levels of inflammatory markers (p < 0.001) and MDA (p < 0.001) while enhancing GSH level (p < 0.001). CONCLUSION: In comparison to individual 5-ASA and D-GLU, combination of drugs significantly diminished colitis severity through their combined anti-inflammatory and antioxidant effects by acting on multiple targets simultaneously. The combination holds remarkable potential in the management of IBD.

Phenolic acid-tethered isoniazid for abrogation of drug-induced hepatotoxicity: design, synthesis, kinetics and pharmacological evaluation.

Morphological and metabolic aberrations in the liver caused by long-term use of anti-tubercular agent isoniazid (INH) have been an issue of great concern in tuberculosis treatment. To resolve this issue, a novel hepatoprotective prodrug strategy was developed by combining the antioxidant property of phenolic acids with INH moiety for probable synergistic effect. In this work, INH was conjugated with phenolic antioxidants using Schotten-Baumann reaction through biocleavable amide linkage. Synthesized prodrugs were characterized by spectral analysis and in vitro release studies were carried out using HPLC. They were found to be stable in acidic (pH 1.2), basic (pH 7.4) buffers, stomach homogenates of rat whereas hydrolyzed significantly (56.03-88.62%) in intestinal homogenates over a period of 6 h. Further their hepatoprotective potential was evaluated in male Wistar rats by performing liver function tests, oxidative stress markers, and histopathology studies. All the prodrugs were effective in abating oxidative stress and re-establishing normal hepatic physiology. Especially the effect of prodrugs of INH with gallic acid and syringic acid in restoring levels of enzymes superoxide dismutase and glutathione peroxidase and abrogating liver damage was noteworthy. The findings of this investigation demonstrated that reported prodrugs can add safety and efficacy to future clinical protocols of tuberculosis treatment.

Investigation of mitigating effect of colon-specific prodrugs of boswellic acid on 2,4,6-trinitrobenzene sulfonic acid-induced colitis in Wistar rats: Design, kinetics and biological evaluation.

AIM: To develop a colon-targeting bioreversible delivery system for ß-boswellic acid (BBA) and explore utility of its prodrugs in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in rats. METHODS: Synthesis of 4 co-drugs of BBA with essential amino acids was achieved by CDI coupling, followed by their spectral characterization. In vitro kinetics were studied by HPLC in aqueous buffers, homogenates of gastrointestinal tract and fecal matter. In vivo kinetic studies were performed in Wistar rat plasma, urine and feces. The prodrugs were screened in TNBS-induced colitis modeled Wistar rats. Statistical significance was assumed at P < 0.05, P < 0.01, P < 0.001 when compared with disease controls using one-way and two-way ANOVAs. RESULTS: Prodrugs were stable in 0.05 mol/L HCl buffer (pH 1.2) and stomach homogenates. Negligible hydrolysis was observed in phosphate buffer and intestinal homogenates. Substantial release (55%-72% and 68%-86%) of BBA was achieved in rat fecal matter and homogenates of colon. In vivo studies of BBA with L-tryptophan (BT) authenticated colon-specific release of BBA. But, surprisingly substantial concentration of BBA was seen to reach the systemic circulation due to probable absorption through colonic mucosa. Site-specifically enhanced bioavailability of BBA could be achieved in colon, which resulted in demonstration of significant mitigating effect on TNBS-induced colitis in rats without inducing any adverse effects on stomach, liver and pancreas. Prodrug of BT was found to be 1.7% (P < 0.001) superior than sulfasalazine in reducing the inflammation to colon among all prodrugs tested. CONCLUSION: The outcome of this study strongly suggests that these prodrugs might have dual applicability to inflammatory bowel disease and chronotherapy of rheumatoid arthritis.

Diacerein-thymol prodrug: in vivo release and pharmacological screening in experimental models of osteoarthritis in Wistar rats.

We have reported the synthesis, characterization, in vitro release profile and preliminary pharmacological investigations of an antioxidant mutual prodrug of diacerein with thymol in our earlier communication. The present work reports the results of in vivo release studies and extensive pharmacological evaluation of this prodrug in collagenase- induced osteoarthritis and monosodium iodoacetate- induced hyperalgesia in Wistar rats. In vivo release was thoroughly studied in Wistar rats upon oral administration of the prodrug. In rat blood, release of 92.7% of diacerein and 20.5% of thymol was observed. From these studies we hypothesized that activation of prodrug could be mediated by physiological pH of blood (7.4) and serum esterases. Pharmacological screening of prodrug in collagenase and monoiodoacetate-induced osteoarthritis at a dose of 6.8 mg/kg, (BID) exhibited significant reduction in knee diameter (p<0.001), increase in paw withdrawal latency (p<0.001), and locomotor activity (p<0.001) with significantly higher anti-inflammatory and anti-osteoarthritic activities as compared to parent drug. The biochemical studies indicated a significant step-up in glucosaminoglycan level (p<0.001) and reduction in the C-reactive protein (p<0.001) and sulfated alkaline phosphatase levels (p<0.001). The histopathological and radiological studies confirmed the additive anti-osteoarthritic effect of prodrug as compared to plain diacerein. Antioxidant potential of prodrug was significantly more (p<0.001) while ulcer index was significantly lower (p<0.01) than diacerein. Interestingly, the diarrhea observed in diacerein- treated animals was not evident in animalstreated with prodrug, thymol and their physical mixture. Our findings indicate promising potential of this antioxidant prodrug to be used for long-term and safer management of OA.

Colon-specific prodrugs of 4-aminosalicylic acid for inflammatory bowel disease.

Despite the advent of biological products, such as anti-tumor necrosis factor-α monoclonal antibodies (infliximab and adalimumab), for treatment of moderate to severe cases of inflammatory bowel disease (IBD), most patients depend upon aminosalicylates as the conventional treatment option. In recent years, the increased knowledge of complex pathophysiological processes underlying IBD has resulted in development of a number of newer pharmaceutical agents like low-molecular-weight heparin, omega-3 fatty acids, probiotics and innovative formulations such as high-dose, once-daily multi-matrix mesalamine, which are designed to minimize the inflammatory process through inhibition of different targets. Optimization of delivery of existing drugs to the colon using the prodrug approach is another attractive alternative that has been utilized and commercialized for 5-aminosalicylic acid (ASA) in the form of sulfasalazine, balsalazide, olsalazine and ipsalazine, but rarely for its positional isomer 4-ASA - a well-established antitubercular drug that is twice as potent as 5-ASA against IBD, and more specifically, ulcerative colitis. The present review focuses on the complete profile of 4-ASA and its advantages over 5-ASA and colon-targeting prodrugs reported so far for the management of IBD. The review also emphasizes the need for reappraisal of this promising but unexplored entity as a potential treatment option for IBD.

Carrier-linked mutual prodrugs of biphenylacetic acid as a promising alternative to bioprecursor fenbufen: design, kinetics, and pharmacological studies.

Novel mutual prodrugs of biphenylacetic acid were designed as a promising gastro-protective alternative to fenbufen. Biphenyacetic acid was covalently linked with two non-essential amino acids (D-phenylalanine and glycine) possessing wound healing, analgesic, and anti-inflammatory properties. The prodrugs exhibited good stability in stomach homogenates while hydrolytic release of biphenylacetic acid was observed in phosphate buffer, small intestinal homogenates, and 80% human plasma. In vivo behavior of prodrugs on oral administration to Wistar rats demonstrated 33-45% release of biphenylacetic acid in blood over a period of 24 h indicating passage of intact prodrugs to colon, colonic release of parent drug followed by its absorption through colonic mucosa into systemic circulation. Prodrugs were extensively evaluated for analgesic, anti-inflammatory, anti-arthritic, and ulcerogenic activities. Biochemical, haemetological, histopathological, and radiological studies were also performed. Conversion of bioprecusor fenbufen into mutual carrier-linked prodrugs proved to be promising alternative in terms of reduced ulcerogenic propensity, longer duration of analgesia, enhanced/prolonged anti-inflammatory activity, and superior anti-arthritic effect. These prodrugs could be developed further for chronotherapy of rheumatoid arthritis.

Disease-modifying effect of anthraquinone prodrug with boswellic acid on collagenase-induced osteoarthritis in Wistar rats.

Diacerein and its active metabolite rhein are promising disease modifying agents for osteoarthritis (OA). Boswellic acid is an active ingredient of Gugglu; a herbal medicine commonly administered in osteoarthritis. Both of them possess excellent anti-inflammatory and anti-arthritic activities. It was thought interesting to conjugate rhein and boswellic acid into a mutual prodrug (DSRB) and evaluate its efficacy on collagenase-induced osteoarthritis in rats wherein the conjugate, rhein, boswellic acid and their physical mixture, were tested based on various parameters. Oral administration of 3.85 mg of rhein, 12.36 mg of boswellic acid and 15.73 mg of DSRB which would release equimolar amounts of rhein and boswellic acid, exhibited significant restoration in rat body weight as compared to the untreated arthritic control group. Increase in knee diameter (mm), due to edema was observed in group injected with collagenase, which reduced significantly with the treatment of conjugate. The hematological parameters (Hb, RBC, WBC and ESR) and biochemical parameters (CRP, SALP, SGOT and SGPT) in the osteoarthritic rats were significantly brought back to normal values on treatment with conjugate. It also showed better anti-ulcer activity than rhein. Further the histopathological studies revealed significant anti-arthritic activity of conjugate when compared with the arthritic control group. In conclusion, the conjugate at the specified dose level of 15.73 mg/kg, p. o. (BID) showed reduction in knee diameter and it could significantly normalize the hematological and biochemical abnormalities in collagenase-induced osteoarthritis in rats. Further the histopathological studies confirmed the additive anti-arthritic effect of DSRB as compared to plain rhein.